Rebreather World - View Single Post - Article from COMEX Scientific Director on rebreathers, decompression and Penny Glover

SFM · 24th May 2006, 09:42

PMR: Isn’t it too easy to blame tables found on the Net when none is available on the market in France?
BG: It’s true it’s a real conscience issue. Let me state that the tables from Buddy are totally valid as long as the dive durations are short. Let me repeat: around 80m all the problems arise for durations over 15 minutes. As well, all-in-all, one must be aware that the deeper one dives, the riskier it becomes…

PMR: On this point, in statistical terms, do we have any idea of accidents risks with existing tables?
BG: Jean-Pierre Imbert, when he used to work for COMEX, realized a thorough study on the topic. Divers must know that one has to consider the amount of gas(es) to eliminate, an amount that is a function of the depth and the square root of the time spent at the bottom. One’s organism has to eliminate that(those) gas(es) and by nature it has its physiological limits. It requires time which cannot be reduced with impunity. Tables that can be downloaded like Varying Permeability Model (VPM) or Reduce Gradient Bubble Model (RGBM) correspond to decompression times we were using more than 30 years ago. The risk was then evaluated at 10%. With the current COMEX tables, for any depth and duration, we divided this risk by 10, meaning less than 1% accident rate. For comparison purposes, the risk for leisure/hobby diving is around 0.01% to 0.001% as long as one stays within the security curve… As soon as one reaches 20 to 30 minutes at 40m, the risk climbs to 0.1% and for 20 minutes at 60m we reach the 1% ratio, identical to what we currently have in our trimix tables… To sum up, one should be reasonable and be content with diving for less than 20 minutes at 60m on air and for trimix, less than 15 minutes at 80m. Ten more minutes yield a huge price to pay in terms of decompression. Dr (MD) Eric Bergman has noted that the number of tech divers treated for a decompression accident has been very high during the summer of 2005…

24th May 2006, 09:42	#6 (permalink)
SFM New Member Current Rebreather/s: Not Bought Yet Other Rebreather/s: Not Bought Yet Join Date: May 2006 Location: West Coast Posts: 11	Re: Article from COMEX Scientific Director on rebreathers, decompression and Penny Gl PMR: Isn’t it too easy to blame tables found on the Net when none is available on the market in France? BG: It’s true it’s a real conscience issue. Let me state that the tables from Buddy are totally valid as long as the dive durations are short. Let me repeat: around 80m all the problems arise for durations over 15 minutes. As well, all-in-all, one must be aware that the deeper one dives, the riskier it becomes… PMR: On this point, in statistical terms, do we have any idea of accidents risks with existing tables? BG: Jean-Pierre Imbert, when he used to work for COMEX, realized a thorough study on the topic. Divers must know that one has to consider the amount of gas(es) to eliminate, an amount that is a function of the depth and the square root of the time spent at the bottom. One’s organism has to eliminate that(those) gas(es) and by nature it has its physiological limits. It requires time which cannot be reduced with impunity. Tables that can be downloaded like Varying Permeability Model (VPM) or Reduce Gradient Bubble Model (RGBM) correspond to decompression times we were using more than 30 years ago. The risk was then evaluated at 10%. With the current COMEX tables, for any depth and duration, we divided this risk by 10, meaning less than 1% accident rate. For comparison purposes, the risk for leisure/hobby diving is around 0.01% to 0.001% as long as one stays within the security curve… As soon as one reaches 20 to 30 minutes at 40m, the risk climbs to 0.1% and for 20 minutes at 60m we reach the 1% ratio, identical to what we currently have in our trimix tables… To sum up, one should be reasonable and be content with diving for less than 20 minutes at 60m on air and for trimix, less than 15 minutes at 80m. Ten more minutes yield a huge price to pay in terms of decompression. Dr (MD) Eric Bergman has noted that the number of tech divers treated for a decompression accident has been very high during the summer of 2005… Last edited by SFM : 24th May 2006 at 10:14.
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